Fry3DX 0.4: an easy 3D modeller

Shapes with live settings, shape editing, knife and hole tools, drawing
shapes onto other objects, combining objects (add / subtract / overlap),
copies, thickness, painting with stickers and layers, a Layout tab, a
Print tab with checks, packed .fry files with autosave, export to GLB,
glTF, FBX, OBJ, 3MF, STL and PLY, folders in Layers, its own crash
screen, and a website for GitHub Pages in docs/.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NMSrd5oe1GpUD7E6d825KP

engine/shaders/sky.vert

@@ -0,0 +1,10 @@
+#version 460
+// The sky: a full-screen triangle on the far plane, drawn where nothing else is (depth test
+// less-or-equal against the cleared 1.0).
+#include "backend.glsl"
+layout(location = 0) out vec2 v_ndc;
+void main() {
+    vec2 uv = vec2((VERTEX_ID << 1) & 2, VERTEX_ID & 2);
+    v_ndc = uv * 2.0 - 1.0;
+    gl_Position = vec4(v_ndc, 1.0, 1.0);
+}